This formula refers to the multiplication rule of rational numbers, which means that two numbers are multiplied, the same sign is positive, different signs are negative, and any number is multiplied by 0 to get 0. In fact, this formula is adapted according to the rules of multiplication operation, which is beneficial to memory and application.
Multiplication rule of rational numbers:
1, the same sign is positive, the different sign is negative, and the absolute value is multiplied.
Any number multiplied by zero will get zero.
3. Multiply several numbers that are not equal to zero. The sign of the product is determined by the number of negative factors. When there are odd negative factors, the product is negative, and when there are even negative factors, the product is positive.
When several numbers are multiplied, if one factor is zero, the product is zero.
5. Multiply several numbers that are not equal to zero, first determine the sign of the product, and then multiply it by the absolute value.
Rational number division:
There is also "rational number division", which is an incomplete inverse operation of rational number multiplication. The operation of finding another factor by knowing the product of two numbers and one of them is called division.
Let A and B be two rational numbers, b≠0, and A divided by B is to find a number X, so that X = A, where X is called the quotient obtained by dividing A by B, which is marked as a÷b, A is called the dividend and B is called the divisor.